The present invention concerns an optical guide comprising an injection zone intended to inject a light signal into the optical guide and an extraction zone intended to provide the light signal after transport by the optical guide.
Typically, an optical guide comprises a guidance zone in which the light signal is transported by reflection from the injection zone to the extraction zone. The most usual case is where the light signal is reflected successively on two parallel flat faces of a slide. The distance between the external faces of the optical guide on which the light signal is reflected from the injection zone to the extraction zone is called the thickness of the optical guide.
The image, or light signal, to be transported is injected into the optical guide thanks to an injection device. The image consists of a light beam issuing from a source that may be a matrix of LCD (Liquid Cristal Display) pixels illuminated by a light source. It may also be a matrix of OLED (Organic Light-Emitting Diode) pixels. An optical system based on lenses enables projecting this image in the form of a collimated beam, which is then introduced into the optical guide via the injection zone.
The size of the injection zone is dependent on the thickness of the optical guide, which itself is dependent on the size of the extraction zone and the required resolution, and therefore the overall size of the injection device is such too.